CHICAGO -- The Cubs' second-half offensive surge continued on Saturday at Wrigley Field as Rene Rivera smacked his first career grand slam, Anthony Rizzo reached 100 RBIs with a bases-clearing triple and Javier Baez added a solo home run and RBI double to post a 14-12 victory over the Braves for Chicago's sixth straight win.

It wasn't easy, as the Braves scored eight runs in the final three innings. Cubs manager Joe Maddon said he felt the momentum starting to shift in the ninth, and he had to call upon closer Wade Davis in a non-save situation to get the final two outs.

"Give them credit -- they were working some good at-bats," Maddon said of the Braves.

Maddon on pulling out the win

ATL@CHC: Maddon discusses winning the wild 14-12 game

Cubs manager Joe Maddon discusses the various factors that led the Cubs pulling out the win against the Braves in a wild affair at Wrigley

Jon Lester, making his first start since Aug. 17 after being sidelined with left shoulder fatigue, served up three home runs, including back-to-back shots on consecutive pitches to Freddie Freeman and Matt Kemp in the third, but he held on for five innings for the win. Freeman added an RBI double in the eighth.

"It was good to get back out there," Lester said.

Lester gets out of the 1st

ATL@CHC: Lester escapes the bases-loaded jam

Jon Lester forces Kurt Suzuki to pop out and escapes a bases-loaded jam in the top of the 1st inning

"The last inning, everything came together," Maddon said of the left-hander. "I talked to him in the dugout after the fourth, and he said, 'I feel great.'"

Rivera launched his homer in the second off Lucas Sims, who was making his seventh start, which is how many postseason starts Lester has made in 2015 and '16. The Cubs added five more runs in the fourth on Rizzo's three-run triple, plus Baez's RBI double and Jason Heyward's RBI single. Heyward also hit a solo homer with two outs in the eighth.

Heyward's solo home run

ATL@CHC: Heyward hammers a solo homer to right field

Jason Heyward launches a solo home run to deep right field, extending the Cubs' lead to 14-9 in the 8th inning

With the win, Chicago is now a season-high 15 games over .500 and 6-0 vs. Atlanta. The Cubs have a 4 1/2-game lead over the Brewers in the National League Central.

At the All-Star break, the Cubs had scored as many runs as they had allowed (399). Since then, they have a plus-98 run differential, and their second-half run total of 292 leads the Majors. This is the sixth time in 19 games since Aug. 14 the Cubs have scored 10 or more runs.

"We have a good team, a good young team that has picked up a lot of experience over the last two years," Rizzo said. "Guys have been chipping away and playing loose now, and it's fun to see."

Rizzo on the Cubs' win

ATL@CHC: Rizzo talks about the win over the Braves

Anthony Rizzo joins the broadcast and discusses his big bases-clearing triple in the Cubs' wild 14-12 win over the Braves

Braves rookie middle infielders Dansby Swanson and Ozzie Albies both recorded three hits. But their contributions weren't enough to overcome a pitching staff that surrendered 12 hits and issued six walks. Sims was charged with seven earned runs as he lasted just three-plus innings.

"You can't pitch like we did and expect to win any ballgames," Braves manager Brian Snitker said. "It wasn't any good from the get-go, and it wasn't real good as we went. It's good that we came back and scored the runs that we did, but we just made way, way too many mistakes."

Snitker on the 14-12 loss

ATL@CHC: Snitker talks failed 9th-inning comeback

Braves manager Brian Snitker discusses the team's 9th-inning comeback attempt that fell just short in the team's 14-12 loss

MOMENTS THAT MATTEREDGrand time: The Cubs loaded the bases with one out in the second against Sims, and Rivera hit an 0-2 pitch 387 feet down the left-field line. It was Rivera's ninth homer this season, but his first since joining the Cubs on Aug. 19, when he was acquired off waivers from the Mets. It was the Cubs' sixth grand slam this season. Rivera tipped his cap to the crowd from the dugout after the slam.

Rivera's first career grand slam

ATL@CHC: Rivera belts grand slam, bullpen celebrates

Rene Rivera crushes his first career grand slam to give the Cubs an early 4-0 lead as the bullpen celebrates in the 2nd inning #PapaSlam

"I was trying to just get something in the air, and bring one run home," Rivera said. "I wasn't thinking, 'Hit a homer,' just drive something to the outfield and get a fly ball or base hit and drive in one and keep the line moving. He threw a curveball and it hung, and I put a good swing on it and hit it out." More >

Homer happy: The Braves loaded the bases against Lester in the first inning, but he escaped that mess. With one out in the third, Albies singled and Freeman launched the first pitch he saw into the left-field bleachers for his 24th home run. Kemp then hit Lester's next pitch into the bleachers to pull within one run. Rio Ruiz added another homer off Lester in the Braves' fourth.

Freeman's two-run jack

ATL@CHC: Freeman slugs a two-run homer to left field

Freddie Freeman drives a two-run home run to left field and puts the Braves on the board in the 3rd inning

Freeman recorded two extra-base hits, but he struck out as the potential tying run to end the game.

"It's always a little too late, and we always come up short," Freeman said. "At least we gave them a game and gave them a little scare at the end." More >

QUOTABLE
"The curveball on the grand slam was one of those that as soon as you throw it, you just want to reel it back or hope maybe it's so bad they don't even swing. That's on me. I kind of set the tone. The guys did awesome to battle back. I didn't get us off to a very good start, and it kind of cost us the ballgame." -- Sims

"There are oil paintings, there's paint by number, and there's the Dick Tracy glitter stuff. I've got that [game as a] paint by agonizing numbers. It was difficult, but we won it and did a lot of good things." -- Maddon

SOUND SMART WITH YOUR FRIENDS
Rizzo's bases-clearing triple gave him 100 RBIs for the season, and he's the fourth player in Cubs history with three seasons of 30 homers, 30 doubles and 100 RBIs. Hack Wilson did so four times (1927-30), Billy Williams three times (1965, '70, '72), and Sammy Sosa three times (1997, 2000-01). More >

Rizzo's bases-clearing triple

ATL@CHC: Rizzo collects 100th RBI on three-run triple

Anthony Rizzo lines a triple to the right-center field gap to score three runs, notching his 100th RBI of the year in the 4th

Prior to Rivera, the last player to hit a grand slam for his first homer in a Cubs uniform was David DeJesus on May 11, 2012.

The Cubs gave up 12 runs and still won for the first time since Aug. 20, 2002, vs. the Astros, which also ended in a 14-12 Chicago victory.

REPLAY REVIEW
The Braves' attempt to rally in the ninth was fueled by a successful challenge after Swanson was called out on a grounder to second base. After the call was overturned, and Atlanta had runners at the corners. Kurt Suzuki scored on a Matt Adams groundout.

Swanson's single after review

ATL@CHC: Swanson hits infield single, call overturned

Dansby Swanson hits a grounder to second and hustles to beat the throw for an infield single, as the call is overturned in the 9th inning

WHAT'S NEXTBraves:Max Fried will make his first career start when this series finale concludes Sunday at 2:20 p.m. ET. Ranked as the Braves' 10th-best prospect by MLBPipeline.com, the young southpaw made four relief appearances for Atlanta in August.

Cubs:Mike Montgomery, who was 2-0 subbing for Lester, will get another start as the Cubs go with a six-man rotation. On July 19 at Atlanta, Montgomery not only pitched well -- giving up one run on two hits over six innings -- but he hit his first career home run. First pitch on Sunday will be 1:20 p.m. CT from Wrigley Field.